1. Field of the Invention
The present invention relates to a side collision detecting apparatus for a vehicle.
2. Description of the Related Art
Conventionally, a side collision detecting apparatus for a vehicle detects a side collision by using a pressure sensor as described, for example, in JP-A-2007-232566. The pressure sensor is disposed in a side door of the vehicle. When an object collides against a side surface of the vehicle, the pressure sensor detects a change in a pressure in the side door, and thereby the side collision detecting apparatus detects the side collision of the object. If the side collision detecting apparatus detects that the object collides against the side surface of the vehicle, the side collision detecting apparatus outputs a signal to a side airbag system so that a side airbag inflates for protecting an occupant.
As a pressure sensor of a side collision detecting apparatus, a diaphragm pressure sensor can be used. When a diaphragm of the diaphragm pressure sensor is applied with a pressure, the diaphragm is distorted in accordance with the pressure. Thus, the side collision detecting apparatus detects a distortion of the diaphragm due to a change in the pressure for detecting a side collision. The diaphragm may be distorted due to an impact force of a side collision depending on an arranging direction of the pressure sensor. If a distortion of the diaphragm occurs due to an impact force in addition to a change in the pressure in the side door, it is difficult for the pressure sensor to detect the change in the pressure with accuracy. Thus, the side airbag may inflate even in a minor accident for which an inflation of the side airbag is unnecessary.
Since the diaphragm has a mass, it is inevitable that the diaphragm pressure sensor detects an impact force applied to the diaphragm as a change in the pressure. Especially, in a case where the diaphragm is configured by a semiconductor diaphragm including a piezoresistive element and the diaphragm is covered with a resin gel layer for protecting bonding wires, when the diaphragm is applied with an impact force, a mass of the resin gel layer may have a great influence to the distortion of the diaphragm.